>> Odd fault on my Rev D KIM-1 popped up while writing code this afternoon >> (initially I thought I had a bug in my paper tape transmitter) - between >> $0280 >> and $029f, the upper 5 bits are stuck at zero. The rest of the address range >> seems fine. In particular, $0080-$009f, $0180-$019f and $0380-$039f work >> correctly. >> >> This doesn't smell like a bad RAM chip to me or I would think there would be >> a >> bad bit throughout the entire 1K, so I suspect this is a data bus problem but >> I'm not sure where to start looking. Any guesses from the group? >> > Maybe an I/O device is sending on the bus when it should not be. Are there > any > devices that have a register range of XX80 to XX9F?
(By the way, I had a typo in my message: it's the upper *six* bits, not five.) I thought about this, but the KIM is a pretty simple system. The only memory mapped device in that range (really, on the entire unit) are the RIOTs, and their RAM at $1780 is fine and does not echo. The KIM only does address decoding for 8K and echoes the rest, so the same fault is mapped at $2280, $4280, etc. I would think this would still suggest data is the problem. I suppose I could randomly replace the RAM and see what changes but again it seems weird to have a fault so neatly aligned and only in a specific range. -- ------------------------------------ personal: http://www.cameronkaiser.com/ -- Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckai...@floodgap.com -- "I'd love to go out with you, but my personalities each need therapy." -----
